1. Field of the Invention
The present invention relates to a driving support system.
2. Description of the Related Art
When a vehicle is driven in reverse, it is difficult for the vehicle driver to confirm a backside because a dead angle is generated. Therefore, there has been already developed a system which is equipped with an in-vehicle camera for monitoring the vehicle backside, where the dead angle is easy to be generated for the driver, to display an image taken by the camera on a screen of a car navigation system or the like.
However, when a wide angle lens is used in order to display a wide range, a lens strain is generated in the screen image. When compared with a normal lens, an object becomes smaller as the object is separated away from the camera, and it is difficult for the driver to recognize a distance and a space of the vehicle backside from the taken image.
Therefore, there is developed a research on which the screen image of the camera is not simply displayed, but the user-friendly screen image is displayed by utilizing an image processing technology. For example, Japanese Patent Laid-Open Nos. H10-211849 and 2002-87160 disclose a system in which coordinate transformation is performed to the taken image to generate and display a bird's eye view image viewed from above the ground. The driver easily recognizes the distance and the space of the vehicle backside by displaying the bird's eye view image viewed from above the ground.
In the system in which the bird's eye view image is generated and displayed, the easily viewable image viewed from above the ground can be shown to the driver. However, there is a problem that height information of the object is lost and becomes less easy to perceive the object, because the object basically having the height is projected in a plane. Because the coordinate transformation is performed based on the ground, in the object having the height different from that of the ground, a shape of the object cannot correctly be maintained due to a difference in height between the object and the ground.
Particularly, as the object is distant from the vehicle, the small difference in height between the object and the ground emerges remarkably on the bird's eye view image, and the object is displayed as if the object is largely tall. That is, in a region distant from the vehicle, image quality of the bird's eye view image is degraded and the shape of the object is not correctly displayed, which worsens visibility.
Therefore, in the generated bird's eye view image, only the region near the vehicle is displayed while the region distant from the vehicle is eliminated, or the bird's eye view image and the original image are respectively displayed. There is a problem that a view angle is narrowed in the former, and there is a problem that a larger monitor is required in the latter.
A device in which the screen images obtained from multiple cameras are transformed into an all-round bird's eye view image by geometrical transformation to display it on the monitor has been developed as a driving support system for parking. In the device, because the screen image all around the vehicle viewed from above can be shown to the driver, there is an advantage that all the peripheries of the vehicle can be displayed with no dead angle. However, in the bird's eye view image, because an obstacle having the height is also projected to the ground, the height information on the obstacle is lost and the shape of the obstacle is deformed as the obstacle is distant from the vehicle. Further, because a size of a display screen is restricted, the far side cannot sufficiently be displayed in the bird's eye view image.